In-line vessel sealer and divider

ABSTRACT

An endoscopic forceps includes a housing having a shaft attached thereto, the shaft including a pair of jaw members disposed at a distal end thereof. The forceps also includes a drive assembly disposed in the housing which moves the jaw members relative to one another from a first position wherein the jaw members are disposed in spaced relation relative to one another to a second position wherein the jaw members are closer to one another for manipulating tissue. A pair of handles is operatively connected to the drive assembly and the handles are movable relative to the housing to actuate the drive assembly to move the jaw members. Each of the jaw members is adapted to connect to a source of electrical energy such that the jaw members are capable of conducting energy for treating tissue. The forceps also includes a first switch disposed on the housing which is activatable to selectively deliver energy of a first electrical potential to at least one jaw member for treating tissue in a monopolar fashion. A second switch is disposed on the housing and is activatable to selectively deliver energy of a first electrical potential to one jaw member and selectively deliver energy of a second electrical potential to the other jaw member for treating tissue in a bipolar fashion.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.11/540,335, filed Sep. 29, 2006 entitled “IN-LINE VESSEL SEALER ANDDIVIDER” by Dumbauld et al. which claims the benefit of priority to U.S.Provisional Application Ser. No. 60/722,177 filed Sep. 30, 2005 entitled“IN-LINE VESSEL SEALER AND DIVIDER” by Patrick L. Dumbauld, the entirecontents of which being incorporated by reference herein.

BACKGROUND

The present disclosure relates to an electrosurgical forceps and moreparticularly, the present disclosure relates to an elongated endoscopiccombination bipolar and monopolar electrosurgical forceps for sealingand/or cutting tissue.

TECHNICAL FIELD

Electrosurgical forceps utilize both mechanical clamping action andelectrical energy to affect hemostasis by heating tissue and bloodvessels to coagulate, cauterize and/or seal tissue. As an alternative toopen forceps for use with open surgical procedures, many modern surgeonsuse endoscopes and endoscopic instruments for remotely accessing organsthrough smaller, puncture-like incisions. As a direct result thereof,patients tend to benefit from less scarring and reduced healing time.

Endoscopic instruments are inserted into the patient through a cannula,or port, which has been made with a trocar. Typical sizes for cannulasrange from three millimeters to twelve millimeters. Smaller cannulas areusually preferred, which, as can be appreciated, ultimately presents adesign challenge to instrument manufacturers who must find ways to makeendoscopic instruments that fit through the smaller cannulas.

Many endoscopic surgical procedures require cutting or ligating bloodvessels or vascular tissue. Due to the inherent spatial considerationsof the surgical cavity, surgeons often have difficulty suturing vesselsor performing other traditional methods of controlling bleeding, e.g.,clamping and/or tying-off transected blood vessels. By utilizing anendoscopic electrosurgical forceps, a surgeon can either cauterize,coagulate/desiccate and/or simply reduce or slow bleeding simply bycontrolling the intensity, frequency and duration of the electrosurgicalenergy applied through the jaw members to the tissue. Most small bloodvessels, i.e., in the range below two millimeters in diameter, can oftenbe closed using standard electrosurgical instruments and techniques.However, if a larger vessel is ligated, it may be necessary for thesurgeon to convert the endoscopic procedure into an open-surgicalprocedure and thereby abandon the benefits of endoscopic surgery.Alternatively, the surgeon can seal the larger vessel or tissue.

It is thought that the process of coagulating vessels is fundamentallydifferent than electrosurgical vessel sealing. For the purposes herein,“coagulation” is defined as a process of desiccating tissue wherein thetissue cells are ruptured and dried. “Vessel sealing” or “tissuesealing” is defined as the process of liquefying the collagen in thetissue so that it reforms into a fused mass. Coagulation of smallvessels is sufficient to permanently close them, while larger vesselsneed to be sealed to assure permanent closure.

In order to effectively seal larger vessels (or tissue) two predominantmechanical parameters must be accurately controlled—the pressure appliedto the vessel (tissue) and the gap distance between the electrodes ortissue sealing surfaces—both of which are affected by the thickness ofthe sealed vessel. More particularly, accurate application of pressureis important to oppose the walls of the vessel; to reduce the tissueimpedance to a low enough value that allows enough electrosurgicalenergy through the tissue; to overcome the forces of expansion duringtissue heating; and to contribute to the end tissue thickness which isan indication of a good seal. It has been determined that a typical jawgap for fusing vessel walls is optimum between 0.001 and 0.006 inches.Below this range, the seal may shred or tear and above this range thelumens may not be properly or effectively sealed.

With respect to smaller vessels, the pressure applied to the tissuetends to become less relevant whereas the gap distance between theelectrically conductive surfaces becomes more significant for effectivesealing. In other words, the chances of the two electrically conductivesurfaces touching during activation increases as vessels become smaller.

Many known instruments include blade members or shearing members whichsimply cut tissue in a mechanical and/or electromechanical manner andare relatively ineffective for vessel sealing purposes. Otherinstruments rely on clamping pressure alone to procure proper sealingthickness and are not designed to take into account gap tolerancesand/or parallelism and flatness requirements which are parameters which,if properly controlled, can assure a consistent and effective tissueseal. For example, it is known that it is difficult to adequatelycontrol thickness of the resulting sealed tissue by controlling clampingpressure alone for either of two reasons: 1) if too much force isapplied, there is a possibility that the two poles will touch and energywill not be transferred through the tissue resulting in an ineffectiveseal; or 2) if too low a force is applied the tissue may pre-maturelymove prior to activation and sealing and/or a thicker, less reliableseal may be created.

As mentioned above, in order to properly and effectively seal largervessels or tissue, a greater closure force between opposing jaw membersis required. It is known that a large closure force between the jawstypically requires large actuation forces which are necessary to createa large moment about the pivot for each jaw. This presents a designchallenge for instrument manufacturers who must weigh the advantages ofmanufacturing an overly-simplified design against the disadvantages of adesign that may require the user to exert a large closure force toeffectively seal tissue. As a result, designers must compensate forthese large closure forces by either designing instruments with metalpins and/or by designing instruments which at least partially offloadthese closure forces to reduce the chances of mechanical failure andreduce fatigue for the end user (i.e., surgeon).

Increasing the closure forces between electrodes may have otherundesirable effects, e.g., it may cause the opposing electrodes to comeinto close contact with one another which may result in a short circuitand a small closure force may cause pre-mature movement of the tissueduring compression and prior to activation. As a result thereof,providing an instrument which consistently provides the appropriateclosure force between opposing electrode within a preferred pressurerange will enhance the chances of a successful seal. As can beappreciated, relying on a surgeon to manually provide the appropriateclosure force within the appropriate range on a consistent basis wouldbe difficult and the resultant effectiveness and quality of the seal mayvary. Moreover, the overall success of creating an effective tissue sealis greatly reliant upon the user's expertise, vision, dexterity, andexperience in judging the appropriate closure force to uniformly,consistently and effectively seal the vessel. In other words, thesuccess of the seal would greatly depend upon the ultimate skill of thesurgeon rather than the efficiency of the instrument.

It has been found that the pressure range for assuring a consistent andeffective seal is between about 3 kg/cm² to about 16 kg/cm² and,preferably, within a working range of 7 kg/cm² to 13 kg/cm².Manufacturing an instrument which is capable of providing a closurepressure within this working range has been shown to be effective forsealing arteries, tissues and other vascular bundles.

Various force-actuating assemblies have been developed in the past forproviding the appropriate closure forces to effect vessel sealing. Forexample, one such actuating assembly has been developed by Valleylab,Inc. of Boulder, Colo., a division of Tyco Healthcare LP, for use withValleylab's vessel sealing and dividing instrument commonly sold underthe trademark LIGASURE ATLAS®. This assembly includes a four-barmechanical linkage, a spring and a drive assembly which cooperate toconsistently provide and maintain tissue pressures within the aboveworking ranges. U.S. application Ser. No. 10/179,863 entitled “VESSELSEALER AND DIVIDER” (now U.S. Pat. No. 7,101,371), U.S. application Ser.No. 10/116,944 entitled “VESSEL SEALER AND DIVIDER” (now U.S. Pat. No.7,083,618), U.S. application Ser. No. 10/472,295 entitled “VESSEL SEALERAND DIVIDER” (now U.S. Pat. No. 7,101,372) and PCT Application SerialNos. PCT/US01/01890 entitled “VESSEL SEALER AND DIVIDER andPCT/US01/11340 entitled “VESSEL SEALER AND DIVIDER” all describe indetail various operating features of the LIGASURE ATLAS® and variousmethods relating thereto. The contents of all of these applications arehereby incorporated by reference herein.

Other force-actuating mechanisms or assemblies are described incommonly-owned U.S. application Ser. No. 10/460,926 entitled “VESSELSEALER AND DIVIDER FOR USE WITH SMALL TROCARS AND CANNULAS” and U.S.application Ser. No. 10/953,757 entitled “VESSEL SEALER AND DIVIDERHAVING ELONGATED KNIFE STROKE AND SAFETY FOR CUTTING MECHANISM”, theentire contents of both are hereby incorporated by reference herein. Asdescribed therein, simpler and more mechanically advantageous actuatingand drive assemblies are described therein which facilitate grasping andmanipulating vessels and tissue and which reduce user fatigue.

In certain surgical operations, a bipolar forceps is used in combinationwith a monopolar forceps or monopolar coagulator to treat tissue andcontrol bleeding during the surgery. As such and during the course of aparticular operation, a surgeon may be required to substitute amonopolar instrument for the bipolar instrument which would typicallyinvolve substitution through the trocar or cannula. As can beappreciated this may occur on more than one occasion over the course ofthe operation which can be quite time consuming and which mayunnecessarily subject the instruments to possible non-sterileenvironments.

It would be desirous to develop a small, simple and cost effectivecombination bipolar and monopolar instrument which can be utilized withsmall cannulas. Moreover, it would be desirous to provide an instrumentwhich includes an easily manipulatable handle and instrument body whichincludes a mechanically advantageous force-actuating assembly to reduceuser fatigue.

SUMMARY

The present disclosure relates to an endoscopic forceps having a housingwith a shaft attached thereto, the shaft including a pair of jaw membersdisposed at a distal end thereof. The forceps also includes a driveassembly disposed in the housing which is configured to move the jawmembers relative to one another from a first position wherein the jawmembers are disposed in spaced relation relative to one another to asecond position wherein the jaw members are closer to one another formanipulating tissue. A pair of handles is operatively connected to thedrive assembly and the handles are configured to move relative to thehousing to actuate the drive assembly to move the jaw members. Each jawmember is adapted to connect to a source of electrical energy such thatthe jaw members are capable of conducting energy for treating tissue.

A first switch is disposed on the housing and is activatable toselectively deliver energy of a first electrical potential to at leastone jaw member for treating tissue in a monopolar fashion. A secondswitch is disposed on the housing and is activatable to selectivelydeliver energy of a first electrical potential to one jaw member andselectively deliver energy of a second electrical potential to the otherjaw member for treating tissue in a bipolar fashion.

In one embodiment according to the present disclosure, the forceps alsoincludes a knife assembly which is operatively associated with thehousing. The knife assembly is selectively actuatable to advance a knifethrough tissue disposed between the jaw members when the jaw members aredisposed in the second position. In yet another embodiment, at least oneof the jaw members may include a monopolar extension which extendsbeyond the insulative housing of the jaw member to permit delicatedissection of tissue.

In one particularly useful embodiment, at least one of the handlesincludes a knife lockout which prevents the knife assembly from beingactuated when the jaw members are disposed in the second position. Theknife lockout mechanism may include a mechanical interface extendingfrom at least one of the handles. The mechanical interface isdimensioned to impede movement of the knife assembly when the handlesare disposed in a first (i.e., open) position relative to the housingand the mechanical interface is dimensioned to permit actuation of theknife assembly when the handles are disposed in a second positionrelative to the housing.

In another embodiment according to the present disclosure, the forcepsincludes a monopolar lockout which prevents activation of the firstswitch when the jaw members are disposed in the first position. In oneparticularly useful embodiment, the monopolar lockout includes amechanical interface disposed on at least one of the handles whichprevents activation of the first switch when the handles are disposed ina first position relative to the housing and permits activation of thefirst switch when the handles are disposed in a second position relativeto the housing. The monopolar lockout may include a pressure activatedswitch disposed in the housing such that movement of the handles from afirst position relative to the housing to a second position relative tothe housing closes the pressure activated switch to allow activation ofthe first switch.

In still yet another embodiment according to the present disclosure, thehandles of the forceps are disposed on opposite sides of the housing andare movable from a first, spaced position relative to the housing to asecond closer position relative to the housing. The housing may also beconfigured to include a pair of slits defined on opposite sides of thehousing and the handles may be dimensioned to move relative to thehousing within the slits. In one particularly useful embodiment, thehousing includes a longitudinal axis defined therethrough and thehandles are disposed at an angle “α” relative to the longitudinal axisto facilitate handling.

In yet another embodiment according to the present disclosure, anintensity controller is included which regulates the intensity ofelectrosurgical energy to the forceps during activation. In aparticularly useful embodiment, the intensity controller is a slidepotentiometer and is operable only in a monopolar mode.

In still another embodiment, the forceps may include an electricalsafety which regulates the forceps to operating in either a bipolarfashion or a monopolar fashion during any given time. In a particularlyuseful embodiment, the first switch and the second switch areindependently and exclusively activatable relative to one another.

The present disclosure also relates to an electrosurgical system havingan electrosurgical generator and an endoscopic forceps. The forcepsincludes a housing having a shaft attached thereto with a pair of jawmembers disposed at a distal end thereof. The jaw members are adapted toconnect to the electrosurgical generator. The forceps also includes adrive assembly disposed in the housing which moves the jaw membersrelative to one another from a first position wherein the jaw membersare disposed in spaced relation relative to one another to a secondposition wherein the jaw members are closer to one another formanipulating tissue. A pair of handles is operatively connected to thedrive assembly to actuate the drive assembly to move the jaw members.

A first switch is disposed on the housing and is activatable toselectively deliver energy of a first electrical potential to at leastone jaw member for treating tissue in a monopolar fashion. A secondswitch is disposed on the housing and is activatable to selectivelydeliver energy of a first electrical potential to one jaw member andselectively deliver energy of a second electrical potential to the otherjaw member for treating tissue in a bipolar fashion.

In one embodiment, the generator includes a control circuit having asafety circuit which permits independent and exclusive activation of theforceps in either a bipolar or monopolar fashion. The safety circuit maybe electrical or electromechanical and activated upon movement to thepair of handles relative to the housing. The generator may also includea control circuit having an isolation circuit operably connected to thesecond switch which regulates the energy to the jaw members whilebypassing the second switch to protect the integrity of the secondswitch from current overload.

The present disclosure also relates to an endoscopic forceps having ahousing with a shaft attached thereto. The shaft includes a pair of jawmembers disposed at a distal end thereof. Each jaw member is adapted toconnect to a source of electrical energy such that the jaw members arecapable of conducting energy for treating tissue. A drive assembly isdisposed in the housing and is operable to move the jaw members relativeto one another from a first position, wherein the jaw members aredisposed in spaced relation relative to one another, to a secondposition, wherein the jaw members are closer to one another, formanipulating tissue. A pair of handles operatively connects to the driveassembly and is movable relative to the housing to actuate the driveassembly to move the jaw members.

A knife assembly is included which is operatively associated with thehousing. The knife assembly is selectively actuatable to advance a knifethrough tissue disposed between the jaw members when the jaw members aredisposed in the second position. The knife assembly includes at leastone safety mechanism to prevent damaging the knife upon selectiveactuation thereof.

In one embodiment, the safety mechanism includes a mechanical fuse whichfractures upon exertion of excessive force (a force of about 9 lbf orgreater) to actuate the knife assembly. In another embodiment, the knifeassembly includes a pinion gear interdisposed between a set of gearteeth and a track which cooperate to advance the knife distally throughthe jaw members. The mechanical fuse may be operatively associated withthe pinion gear, gear teeth and/or the track. In one particularembodiment, an axle of the pinion gear is designed to fracture uponexcessive force to actuate the knife assembly. In another embodimentaccording to the present disclosure, first and second switches may beincluded to deliver energy to the jaw members as described mentionedabove.

The present disclosure also relates to an endoscopic forceps having ahousing with a shaft attached thereto. The shaft includes a pair of jawmembers disposed at a distal end thereof, each jaw member adapted toconnect to a source of electrical energy such that the jaw members arecapable of conducting energy for treating tissue. A drive assembly isdisposed in the housing and is operable to move the jaw members relativeto one another from a first position, wherein the jaw members aredisposed in spaced relation relative to one another, to a secondposition, wherein the jaw members are closer to one another, formanipulating tissue. A pair of handles is included which operativelyconnects to the drive assembly and is movable relative to the housing toactuate the drive assembly to move the jaw members.

A switch is included which is disposed on the housing and is activatableto selectively deliver energy of a first electrical potential to atleast one jaw member for treating tissue. The switch is operativelycoupled to an intensity control mechanism disposed within the housingwhich is selectively adjustable to regulate the level of electrosurgicalenergy to at least one jaw member. In one embodiment, the intensitycontrol mechanism is selectively adjustable in discreet increments. Inanother embodiment, the intensity control mechanism includes a firstmechanical interface (e.g., a detent) configured to engage a series ofcorresponding mechanical interfaces (e.g., recesses) defined in thehousing to regulate the level of electrosurgical energy in discreetincrements. The detent may be disposed in a cantilevered fashion atopthe intensity control mechanism and the intensity control mechanism maybe disposed atop a railway to facilitate movement thereof.

In yet another embodiment, the intensity control mechanism includes asecond mechanical interface (e.g., a slide bump) that cooperates withthe detent to mechanically engage a circuit board disposed within thehousing at discreet locations when the detent engages a correspondingone of the series of recesses.

The present disclosure also relates to an endoscopic forceps having ahousing with a shaft attached thereto. The shaft includes a pair of jawmembers disposed at a distal end thereof, each jaw member adapted toconnect to a source of electrical energy such that the jaw members arecapable of conducting energy for treating tissue. A drive assembly isdisposed in the housing and is operable to move the jaw members relativeto one another from a first position, wherein the jaw members aredisposed in spaced relation relative to one another, to a secondposition, wherein the jaw members are closer to one another, formanipulating tissue. A pair of handles operatively connects to the driveassembly and is movable relative to the housing to actuate the driveassembly to move the jaw members.

A switch is disposed on the housing and is activatable to selectivelydeliver energy of a first electrical potential to at least one jawmember for treating tissue. First and second toggle links are includedwhich operatively connect each one of the pair of handles to the driveassembly. Each of the toggle links includes first and second anchoringelements, the first anchoring element operatively engaging the handleand the second anchoring element operatively engaging the driveassembly.

In one embodiment, the first and second anchoring elements each includea pair of tapered double tangs which operatively engage the handle andthe drive assembly, respectively, in a snap-fit manner. Each pair ofdouble tangs may include a step at a proximal end thereof for seatingeach pair of double tangs within a respective aperture defined withinthe handle and the drive assembly.

A slot may be defined between each pair double tangs. The slots may beoriented such that the greatest cross sectional area of the double tangsoffsets an applied load on the forceps thereby preventing failure of thetoggle links during actuation of the handles.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject instrument are described herein withreference to the drawings wherein:

FIG. 1A is a top, perspective view of an endoscopic forceps shown in anopen configuration and including a housing, a handle assembly, a shaftand an end effector assembly according to the present disclosure;

FIG. 1B is a top, perspective view of the endoscopic forceps of FIG. 1Ashowing the end effector assembly in a closed configuration according tothe present disclosure;

FIG. 2 is a bottom, perspective view of the endoscopic forceps of FIG.1A;

FIG. 3A is an enlarged left, perspective view of the end effectorassembly of FIG. 1A;

FIG. 3B is an enlarged left, perspective view of the end effectorassembly of FIG. 1B;

FIG. 3C is an enlarged side view of the end effector assembly of FIG.1A;

FIG. 3D is an enlarged end view of the end effector assembly of FIG. 1A;

FIG. 4 is a top, internal perspective view of the forceps of FIG. 1Ashown without a housing cover;

FIG. 5A is an enlarged, top view of the forceps of FIG. 1A showing thedisposition of the internal components when the forceps is in an openconfiguration;

FIG. 5B is an enlarged, top view of the forceps of FIG. 1B showing thedisposition of the internal components when the forceps is in a closedconfiguration;

FIG. 6A is an enlarged perspective view of the internal workingcomponents of the forceps of FIG. 1B showing a knife actuator in anun-actuated position;

FIG. 6B is an enlarged perspective view of the internal workingcomponents of the forceps of FIG. 1B showing a knife actuator beingactuated;

FIG. 7 is an enlarged side view of the knife actuator in an un-actuatedposition;

FIG. 8A is a greatly-enlarged, top cross sectional view of an endeffector of the end effector assembly showing a knife of the knifeactuator in a proximal-most or unactuated position;

FIG. 8B is a greatly-enlarged, top cross sectional view of the endeffector assembly of FIG. 8A showing the position of the knife afteractuation;

FIG. 9A is an enlarged, top view showing the handle assembly in anunactuated position;

FIG. 9B is an enlarged, top view showing the handle assembly afteractuation;

FIG. 10A is a greatly-enlarged, side cross sectional view of the endeffector assembly shown in an open configuration;

FIG. 10B is a greatly-enlarged, side cross sectional view of the endeffector assembly shown in a closed configuration;

FIG. 10C is a greatly-enlarged, front perspective view of a bottom jawmember of the end effector assembly showing the knife of the knifeactuator in a proximal-most or unactuated position;

FIG. 10D is a greatly-enlarged, front perspective view of the bottom jawmember of FIG. 10C showing the position of the knife after actuation;

FIG. 11A is an enlarged, top view similar to FIG. 9B showing the knifeactuator after actuation;

FIG. 11B is a greatly-enlarged, side cross sectional view of the endeffector assembly showing the position of the knife after actuation;

FIG. 12 is top, perspective view of the forceps of FIG. 1B showingrotation of the end effector assembly;

FIG. 13 is a top, perspective view of the forceps with parts separated;

FIG. 14 is an enlarged, perspective view of the housing with partsseparated;

FIG. 15A is a greatly-enlarged, perspective view of the bottom jaw ofthe end effector assembly with parts separated;

FIG. 15B is a greatly-enlarged, perspective view of the top jaw of theend effector assembly with parts separated;

FIG. 16 is an enlarged, perspective view of a circuit board for use withthe forceps according to the present disclosure;

FIG. 17 is a greatly-enlarged, perspective view of the elongated shaftfor housing various moving parts of the drive assembly and knifeassembly;

FIG. 18 is a top, perspective view of an alternate safety lockoutmechanism for use with the forceps of FIG. 1A;

FIG. 19 is a top view of a flex circuit board for use with the forcepsof FIG. 1A;

FIG. 20 is a schematic diagram showing the operational features of asafety switch of the flex circuit board of FIG. 19;

FIG. 21 is an internal perspective view showing the assembly of thesafety switch of FIG. 19 in the housing of the forceps;

FIG. 22A-22C are internal views showing the operational movements of thesafety lockout mechanism of FIG. 18 as the lockout mechanism engages thesafety switch of the flex circuit board;

FIG. 23 is a schematic electrical diagram of the electrical switchingassembly;

FIG. 24 is a computer simulation showing the movement of the anintensity control on the switching assembly;

FIG. 25 is an enlarged view of the intensity control actuator;

FIG. 26 is a computer-simulated, enlarged internal view of the intensitycontrol actuator mechanically engaged within a detent track disposed inthe housing;

FIG. 27 is a computer-simulated, enlarged internal top view of theintensity control actuator mechanically engaged atop a railway definedin the housing;

FIG. 28 is a computer-simulated perspective view showing a taperedtoggle link operatively connecting the drive assembly to a handle of thehandle assembly;

FIG. 29 is an enlarged, perspective view of one embodiment of a togglelink showing a pair double tang anchoring element; and

FIG. 30 is an enlarged top view showing the orientation of a pair ofslots each defined between one of the pair double tang anchoringelements.

DETAILED DESCRIPTION

Turning now to FIGS. 1A-2, one embodiment of a combination endoscopicbipolar and monopolar forceps 10 is shown for use with various surgicalprocedures and generally includes a housing 20, a handle assembly 30, arotating assembly 80, a knife trigger assembly 70 and an end effectorassembly 100 which mutually cooperate to grasp, seal and divide tubularvessels and vascular tissue (FIGS. 10A and 10B). Although the majorityof the figure drawings depict a forceps 10 for use in connection withendoscopic surgical procedures, the present disclosure may be used formore traditional open surgical procedures. For the purposes herein, theforceps 10 is described in terms of an endoscopic instrument; however,it is contemplated that an open version of the forceps may also includethe same or similar operating components and features as describedbelow.

Forceps 10 includes a shaft 12 which has a distal end 16 dimensioned tomechanically engage the end effector assembly 100 and a proximal end 14which mechanically engages the housing 20. Details of how the shaft 12connects to the end effector are described in more detail below. Theproximal end 14 of shaft 12 is received within the housing 20 and theconnections relating thereto are also described in detail below. In thedrawings and in the descriptions which follow, the term “proximal”, asis traditional, will refer to the end of the forceps 10 which is closerto the user, while the term “distal” will refer to the end which isfurther from the user.

Forceps 10 also includes an electrosurgical cable 310 which connects theforceps 10 to a source of electrosurgical energy, e.g., a generator 500(See FIG. 16). Generators such as those sold by Valleylab—a division ofTyco Healthcare LP, located in Boulder Colo. may be used as a source ofboth bipolar electrosurgical energy for sealing vessel and vasculartissues as well as monopolar electrosurgical energy which is typicallyemployed to coagulate or cauterize tissue. It is envisioned that thegenerator 500 may include various safety and performance featuresincluding isolated output, impedance control and/or independentactivation of accessories. The electrosurgical generator 500 may also beconfigured to include Valleylab's Instant Response™ technology whichprovides an advanced feedback system to sense changes in tissuetwo-hundred (200) times per second and adjust voltage and current tomaintain appropriate power. The Instant Response™ technology is believedto provide one or more of the following benefits to surgical procedure:

-   -   Consistent clinical effect through all tissue types;    -   Reduced thermal spread and risk of collateral tissue damage;    -   Less need to “turn up the generator”; and    -   Designed for the minimally invasive environment.

As best show in FIG. 16, cable 310 is divided into cable leads 310 a and310 b which are configured to connect the forceps to the electrosurgicalgenerator 500 by virtue of one or more connectors or by virtue ofseparate so-called “flying leads” which are configured to connect to thegenerator 500 at a single location and provide either bipolar, monopolar(or a combination thereof) energy as desired or based upon theparticular instrument configuration set up by the surgeon prior tosurgery. One example of a universal electrical connector is beingcurrently developed by Valleylab, Inc. of Boulder, Colo. a division ofTyco Healthcare, LP and is the subject of U.S. patent application Ser.No. 10/718,114 entitled “CONNECTOR SYSTEMS FOR ELECTROSURGICALGENERATOR” the entire contents of which is incorporated by referenceherein.

Handle assembly 30 includes two movable handles 30 a and 30 b disposedon opposite sides of housing 20. Handles 30 a and 30 b are movablerelative to one another to actuate the end effector assembly 100 asexplained in more detail below with respect to the operation of theforceps 10.

As best seen in the exploded view of FIG. 13, housing 20 is formed fromtwo (2) housing halves 20 a and 20 b which each include a plurality ofinterfaces 205 which are dimensioned to mechanically align and engageone another to form housing 20 and enclose the internal workingcomponents of forceps 10. It is envisioned that a plurality ofadditional interfaces (not shown) may disposed at various points aroundthe periphery of housing halves 20 a and 20 b for ultrasonic weldingpurposes, e.g., energy direction/deflection points. It is alsocontemplated that housing halves 20 a and 20 b (as well as the othercomponents described below) may be assembled together in any fashionknown in the art. For example, alignment pins, snap-like interfaces,tongue and groove interfaces, locking tabs, adhesive ports, etc. may allbe utilized either alone or in combination for assembly purposes.

Rotating assembly 80 is mechanically coupled to housing 20 and isrotatable approximately 90 degrees in either direction about alongitudinal axis “A” (See FIGS. 1A-2 and 12). Details of the rotatingassembly 80 are described in more detail with respect to FIGS. 12-14.Rotating assembly 80 includes two halves 81 a and 81 b which, whenassembled, form the rotating assembly 80 which, in turn, supports theelongated shaft 12 which houses drive assembly 60 and the knife assembly70. Halves 81 a and 81 b are mechanically engaged to housing 20 atopflanges 82 a and 82 b, respectively, during assembly and may includeother mechanical interfaces dimensioned to securely engage the twohalves 81 a and 81 b of the rotating assembly 80, e.g., alignment pins,snap-fit interfaces, ultrasonic welding points, etc.

As mentioned above, end effector assembly 100 is attached at the distalend 16 of shaft 12 and includes a pair of opposing jaw members 110 and120 (See FIGS. 3A-3D). Handles 30 a and 30 b of handle assembly 30ultimately connect to drive assembly 60 which, together, mechanicallycooperate to impart movement of the jaw members 110 and 120 from an openposition wherein the jaw members 110 and 120 are disposed in spacedrelation relative to one another, to a clamping or closed positionwherein the jaw members 110 and 120 cooperate to grasp tissue (FIGS. 10Aand 10B) therebetween.

It is envisioned that the forceps 10 may be designed such that it isfully or partially disposable depending upon a particular purpose or toachieve a particular result. For example, end effector assembly 100 maybe selectively and releasably engageable with the distal end 16 of theshaft 12 and/or the proximal end 14 of shaft 12 may be selectively andreleasably engageable with the housing 20 and the handle assembly 30. Ineither of these two instances, the forceps 10 would be considered“partially disposable” or “reposable”, i.e., a new or different endeffector assembly 100 (or end effector assembly 100 and shaft 12)selectively replaces the old end effector assembly 100 as needed. As canbe appreciated, the presently disclosed electrical connections may haveto be altered to modify the instrument to a reposable forceps.

Turning now to the more detailed features of the present disclosure asdescribed with respect to FIGS. 1A-16, handles 30 a and 30 b eachinclude an aperture 33 a and 33 b, respectively, defined therein whichenables a user to grasp and move each respective handle 30 a and 30 brelative to one another. Handles 30 a and 30 b also includeergonomically-enhanced gripping elements 39 a and 39 b, respectively,disposed along an outer edge thereof which are designed to facilitategripping of the handles 30 a and 30 b during activation. It isenvisioned that gripping elements 39 a and 39 b may include one or moreprotuberances, scallops and/or ribs to enhance gripping.

As best illustrated in FIGS. 1A and 7, handles 30 a and 30 b areconfigured to extend outwardly on opposite sides from a transverse axis“B” defined through housing 20 which is perpendicular to longitudinalaxis “A”. Handles 30 a and 30 b are movable relative to one another in adirection parallel to axis “B” to open and close the jaw members 110 and120 as needed during surgery. This forceps style is commonly referred toas an “in-line” or hemostat style forceps as compared to a so-called“pistol grip” style forceps or endoscopic instrument. In-line hemostatsor forceps are more commonly manufactured for open surgical proceduresand typically include a pair of shafts having integrally coupled handleswhich are movable relative to one another to open and close the jawmembers disposed at the distal end thereof.

As best illustrated in FIG. 5A and as mentioned above, handles 30 a and30 b mechanically couple to the housing 20 and are movable relative tothe housing (and each other) to affect movement of the jaw members 110and 120 from the open or spaced configuration to a closed position abouttissue. Each handle, e.g., handle 30 a shown in FIG. 7, is alsoconfigured to extend downwardly at an angle alpha (α) relative to thelongitudinal axis “A”. It is envisioned that manufacturing the handles30 a and 30 b to extend in this fashion facilitates and enhancesgripping and manipulation of the forceps 10 during operating conditions.It is envisioned that the angle (α) of the handles 30 a and 30 b offorceps 10 may be adjustable to allow different users to essentially“customize” the handles 30 a and 30 b for a particular use of for aparticular hand size. Alternatively, different forceps 10 may bemanufactured with different pre-fixed angles (α) for use with specificsurgical procedures, for particular hand sizes (i.e., small, medium andlarge) and/or for other surgical purposes. It is further contemplatedthat in a particularly useful embodiment, the angle (α) of the handleranges from about zero degrees (0°) degrees to about thirty-five degrees(35°).

As best seen in FIGS. 5A, 5B, 13 and 14, the distal end 34 and 37 ofeach handle 30 a and 30 b, respectively, is selectively moveable aboutpivot pins 34 a and 34 b attached to a distal end 21 of the housing 20.As explained in more detail below, movement of the handles relative toone another imparts movement of the jaw members 110 and 120 relative toone another. The distal ends 34 and 37 are configured to includecomplimentary gear teeth 34 a′ and 34 b′ which are configured tointermesh with one another to facilitate consistent movement of thehandle members 30 a and 30 b relative to one another and to enhanceactuation of the jaw members 110 and 120.

In FIG. 14, the proximal end 30 a′ and 30 b′ of the each handle 30 a and30 b, respectively, includes a flange 31 a and 31 b which extends fromthe proximal end 30 a′ and 30 b′ of each handle 30 a and 30 b towardsthe housing 20. Each of the flanges 31 a and 31 b includes an aperture36 c′ and 36 d′ disposed therein for receiving an end 36 c and 36 d of atoggle link 35 a and 35 b, respectively. The opposite ends 36 a and 36 bof the toggle links 35 a and 35 b are configured to attached to anactuating or drive collar 69 of the drive assembly 60 throughcorresponding apertures 36 a′ and 36 b′ defined therethrough. It isenvisioned that the toggle links 35 a and 35 b may be dimensioned in agenerally S-shaped configuration to attach the handles 30 a and 30 b tothe drive collar 69 or the toggle links 35 a and 35 b may be generallyU-shaped (as disclosed) to accomplish this purpose. It is contemplatedthat dimensioning the toggle links 35 a and 35 b in a U-shapedconfiguration may reduce buckling during actuation.

In one envisioned embodiment, the toggle links, e.g., toggle link 35 a′,are generally symmetrical and include snap-like mechanical interfaces atthe distal ends thereof to facilitate manufacture and assembly. Moreparticularly and as best shown in FIGS. 28-30, link 35 a′ includes twodouble tang anchoring elements 36 d″ and 36 b″ at opposite ends thereofwhich are designed to correspondingly engage the drive collar 69 to arespective handle, e.g., 30 b. In other words, anchor element 36 d″ isconfigured to engage aperture 36 d′ of the handle 30 b and anchorelement 36 b″ is configured to engage aperture 36 b′ of drive collar 69to link the drive collar 69 to handle 30 b.

As can be appreciated, the geometry of each respective double tanganchor elements 36 b″ and 36 d″ includes a pair of tapered double tangs37 a, 37 b and 37 c, 37 d. Each pair of double tangs 37 a, 37 b and 37c, 37 d, respectively, includes a step 39 a′, 39 b′ and 39 c′ and 39 d′,respectively, at a proximal end thereof. Each pair of opposing tangs 37a, 37 b and 37 c, 37 d includes a slot 38 a and 38 b, respectively,defined therebetween to allow each tang 37 a, 37 b and 37 c, 37 d todeflect inwardly to reduce the cross section of the anchoring element 36d″ and 36 b″. As can be appreciated, upon assembly into a correspondingaperture, e.g., 36 d and 36 b, the taper of each tang 37 a, 37 b and 37c, 37 d forces each tang 37 a, 37 b and 37 c, 37 d inwardly to reducethe cross section of each anchoring element 36 d″ and 36 b″ tofacilitate engagement of the anchoring elements 36 d″ and 36 b″ within acorresponding aperture 36 d′ and 36 b′. Once the double tangs 37 a, 37 band 37 c, 37 d are engaged within the respective apertures 36 d″ and 36b″ past steps 39 a′, 39 b′ and 39 c′ and 39 d′, the tangs 37 a, 37 b and37 c, 37 d spring outwardly to engage and seat the respective anchoringelement 36 d″ and 36 b″ within the corresponding apertures 36 d′ and 36b′. Once assembled, the slots 38 a and 38 b are preferably oriented suchthat the greatest cross sectional area of each anchoring element 36 d″and 36 b″, i.e., the area with the most material, resides in thedirection of the load when applied to close the jaw members 110 and 120(See FIGS. 28 and 30). This prevent the toggle links 35 a′ and 35 b′from failing due to an overstressed condition or repeated use.

As can be appreciated, movement of the handles 30 a and 30 b from anopen or spaced apart configuration to a closed position towards thehousing forces the actuating collar 69 proximally against a spring 63which, in turn, translates a drive shaft 17 proximally to close the jawmembers 110 and 120 (see FIGS. 7-9). The operative relationship of thedrive collar 69 and the handle assembly 30 is explained in detail belowwith respect to the operation of the forceps 10.

The handles 30 a and 30 b force the toggle links 35 a and 35 b to rotatealong the longitudinal axis “A” beyond a parallel orientation with shaft17 or longitudinal axis “A” such that, upon release, the force of spring63 maintains the toggle links 35 a and 35 b in an over center or anover-extended (or past parallel) configuration thereby locking thehandles 30 a and 30 b (and therefore the jaw members 110 and 120)relative to one another (FIG. 9B). Movement of the handles 30 a and 30 baway from one another (and the housing 20) unlocks and opens the handles30 a and 30 b and, in turn, the jaw members 110 and 120 for subsequentgrasping or re-grasping of tissue. In one embodiment, the handles 30 aand 30 b may be biased in an open configuration to facilitate handlingand manipulation of the forceps within an operative field. Variousspring-like mechanisms are contemplated which may be utilized toaccomplish this purpose.

Handle 30 a also includes a locking flange 32 which is disposed betweenthe distal and proximal ends 34 a′ and 30 a′, respectively, whichextends towards the housing 20 and moves relative thereto when handle 30a is actuated. Locking flange 32 includes a lockout element 32′ (FIG.14) which is dimensioned to prevent actuation of the knife assembly 70when handle 30 a is disposed in a spaced-apart or open configuration.Actuation or movement of the handle 30 a towards the housing 20disengages the lockout element 32 to allow movement of the knifeassembly 70 (e.g., collar 74) to separate tissue as explained in moredetail below.

Movable handles 30 a and 30 b are designed to provide a distinctlever-like mechanical advantage over conventional handle assemblies dueto the unique position of the toggle links 35 a and 35 b which, whenactuated, rotate along the longitudinal axis “A” to displace theactuation or drive collar 69. In other words, it is envisioned thatenhanced mechanical advantage for actuating the jaw members 110 and 120is gained by virtue of the unique position and combination of severalinter-cooperating elements (i.e., opposing handles 30 a, 30 b, togglelinks 35 a, 35 b and gear teeth located at the distal ends 34 and 37 ofthe handle members 30 a, 30 b, respectively) which reduce the overalluser forces necessary to obtain and maintain the jaw members 110 and 120under ideal operating pressures of about 3 kg/cm² to about 16 kg/cm². Inother words, it is envisioned that the combination of these elements andtheir positions relative to one another enables the user to gainlever-like mechanical advantage to actuate the jaw members 110 and 120enabling the user to close the jaw members 110 and 120 with lesser forcewhile still generating the required forces necessary to effect a properand effective tissue seal. The details relating to the various movementsof the above-identified elements are explained below with respect to theoperation of the forceps 10.

As shown best in FIGS. 3A-3D, 10A-10D and 15A-15D, the end effectorassembly 100 includes opposing jaw members 110 and 120 which cooperateto effectively grasp tissue for sealing purposes. The end effectorassembly 100 is designed as a bilateral assembly, i.e., both jaw members110 and 120 pivot relative to one another about a pivot pin 185 disposedtherethrough.

A reciprocating drive sleeve 17 (See FIG. 17) is slidingly disposedwithin the shaft 12 and is remotely operable by the drive assembly 60 asexplained in more detail below. Drive sleeve 17 includes a bifurcateddistal end composed of halves 17 a and 17 b, respectively, which definea cavity 17′ therebetween for receiving jaw members 110 and 120. Moreparticularly and as best illustrated in FIGS. 15A and 15B, jaw members110 and 120 include proximal flanges 113 and 123 (See FIGS. 15A and15B), respectively, which each include an elongated angled slot 181 aand 181 b, respectively, defined therethrough. A drive pin 180 (SeeFIGS. 10A and 10B) mounts jaw members 110 and 120 to the end of arotating shaft 18 and within cavity 17′ disposed at the distal ends 17 aand 17 b of drive sleeve 17.

Upon actuation of the drive assembly 60, the drive sleeve 17reciprocates which, in turn, causes the drive pin 180 to ride withinslots 181 a and 181 b to open and close the jaw members 110 and 120 asdesired. The jaw members 110 and 120, in turn, pivot about pivot pin 185disposed through respective pivot holes 186 a and 186 b disposed withinflanges 113 and 123. As can be appreciated, squeezing handles 30 a and30 b toward the housing 20 pulls drive sleeve 17 and drive pin 180proximally to close the jaw members 110 and 120 about tissue 420 graspedtherebetween and pushing the sleeve 17 distally opens the jaw members110 and 120 for grasping purposes.

As best shown in FIG. 15B, jaw member 110 also includes a support base119 which extends distally from flange 113 and which is dimensioned tosupport an insulative plate 119′ thereon. Insulative plate 119′, inturn, is configured to support an electrically conductive tissueengaging surface or sealing plate 112 thereon. It is contemplated thatthe sealing plate 112 may be affixed atop the insulative plate 119′ andsupport base 119 in any known manner in the art, snap-fit, over-molding,stamping, ultrasonically welded, etc. Support base 119 together with theinsulative plate 119′ and electrically conductive tissue engagingsurface 112 are encapsulated by an outer insulative housing 114. Outerhousing 114 includes a cavity 114 a which is dimensioned to securelyengage the electrically conductive sealing surface 112 as well as thesupport base 119 and insulative plate 119′. This may be accomplished bystamping, by overmolding, by overmolding a stamped electricallyconductive sealing plate and/or by overmolding a metal injection moldedseal plate. All of these manufacturing techniques produce jaw member 110having an electrically conductive surface 112 which is substantiallysurrounded by an insulating substrate 114.

For example and as shown in FIG. 15B, the electrically conductivesealing plate 112 includes a mating portion 112 a which surrounds theperiphery of the sealing plate 112. Flange 112 a is designed to matinglyengage an inner lip 117 of the outer insulator 114. It is envisionedthat lead 325 a extending from circuit board 170 or generator 500 (SeeFIG. 16) terminates within the outer insulator 114 and is designed toelectro-mechanically couple to the sealing plate 112 by virtue of acrimp-like connection 326 a. For example, the insulator 119′,electrically conductive sealing surface 112 and the outer,non-conductive jaw housing 114 are preferably dimensioned to limitand/or reduce many of the known undesirable effects related to tissuesealing, e.g., flashover, thermal spread and stray current dissipation.

It is envisioned that the electrically conductive sealing surface 112may also include an outer peripheral edge which has a pre-defined radiusand the outer housing 114 meets the electrically conductive sealingsurface 112 along an adjoining edge of the sealing surface 112 in agenerally tangential position. At the interface, the electricallyconductive surface 112 is raised relative to the outer housing 114.These and other envisioned embodiments are discussed in co-pending,commonly assigned Application Serial No. PCT/US01/11412 entitled“ELECTROSURGICAL INSTRUMENT WHICH REDUCES COLLATERAL DAMAGE TO ADJACENTTISSUE” by Johnson et al. and co-pending, commonly assigned ApplicationSerial No. PCT/US01/11411 entitled “ELECTROSURGICAL INSTRUMENT WHICH ISDESIGNED TO REDUCE THE INCIDENCE OF FLASHOVER” by Johnson et al., theentire contents of both of which being hereby incorporated by referenceherein.

The electrically conductive surface or sealing plate 112 and the outerhousing 114, when assembled, form a longitudinally-oriented slot 115 adefined therethrough for reciprocation of the knife blade 190. It isenvisioned that the knife channel 115 a cooperates with a correspondingknife channel 115 b defined in jaw member 120 to facilitate longitudinalextension of the knife blade 190 along a preferred cutting plane toeffectively and accurately separate the tissue along the formed tissueseal. As best illustrated in FIGS. 8A, 8B, 15A and 15B, knife channel115 runs through the center of the jaw members 110 and 120,respectively, such that a blade 190 from the knife assembly 70 can cutthe tissue grasped between the jaw members 110 and 120 when the jawmembers 110 and 120 are in a closed position. More particularly and asmentioned above with respect to the discussion of the handle assembly30, handle 30 a includes a lockout flange which prevents actuation ofthe knife assembly 70 when the handle 30 a is open thus preventingaccidental or premature activation of the blade 190 through the tissue.

As explained above and as illustrated in FIGS. 15A and 15B, the knifechannel 115 is formed when the jaw members 110 and 120 are closed. Inother words, the knife channel 115 includes two knife channelhalves—knife channel half 115 a disposed in sealing plate 112 of jawmember 110 and knife channel half 115 b disposed sealing plate 122 ofjaw member 120. It is envisioned that the knife channel 115 may beconfigured as a straight slot with no degree of curvature which, inturn, causes the knife 190 to move through the tissue in a substantiallystraight fashion. Alternatively, the knife channel 115 may bedimensioned to include some degree of curvature to cause the knife 190to move through tissue in a curved fashion. Insulating plate 119′ alsoforms part of the knife channel 115 and includes a channel 115 a′defined therein which extends along insulating plate 119′ and whichaligns in vertical registration with knife channel half 115 a tofacilitate translation of distal end 192 of the knife 190 therethrough.

The electrically conductive sealing plate 112 of jaw member 110 alsoincludes a monopolar extension 112 a which allows a surgeon toselectively coagulate tissue when disposed in a monopolar activationmode as explained in more detail below with respect to the operation ofthe forceps 10. Monopolar extension 112 a is preferably integrallyassociated with conductive sealing plate 112 but may also be selectivelyextendible depending upon a particular purpose. The shape and dimensionof the monopolar extension 112 a may be dimensioned to match the overallcontour of the curving contour of the jaw member 110 or the jaw housing114. The edges of the monopolar extension 112 a may be dimensioned toinclude radii specifically dimensioned to reduce current density alongthe edges thereof, e.g., smooth curves and transition points. Thethickness of the monopolar extension 112 a is preferably within a rangeof about 0.010 inches +/−0.005 inches. The width of the monopolarextension 112 a is preferably about 0.084 inches +/−0.010 inches topermit the creation of an enterotomy that the jaw member(s) may passtherethrough for the purposes of mechanically spreading tissue. Thelength is preferably about 0.040 inches +/−0.010 inches. Commonly-ownedU.S. application Ser. No. 10/970,307 entitled “BIPOLAR FORCEPS HAVINGMONOPOLAR EXTENSION” and U.S. application Ser. No. 10/988,950 entitled“BIPOLAR FORCEPS HAVING MONOPOLAR EXTENSION” disclose variousembodiments of a monopolar extension which may be configured for usewith forceps 10 of the present disclosure. The entire contents of bothof these applications are hereby incorporated by reference herein.

Jaw member 120 includes similar elements to jaw member 110 such as jawhousing 124 which encapsulates a support plate 129, an insulator plate129′ and an electrically conductive sealing surface 122. Likewise, theelectrically conductive surface 122 and the insulator plate 129′, whenassembled, include respective longitudinally-oriented knife channels 115a and 115 a′ defined therethrough for reciprocation of the knife blade190. As mentioned above, when the jaw members 110 and 120 are closedabout tissue, knife channels 115 a and 115 b form a complete knifechannel 115 to allow longitudinal extension of the knife 190 in a distalfashion to sever tissue along a tissue seal. It is also envisioned thatthe knife channel 115 may be completely disposed in one of the two jawmembers, e.g., jaw member 120, depending upon a particular purpose. Itis also envisioned that jaw member 120 may be assembled in a similarmanner as described above with respect to jaw member 110.

As best seen in FIG. 15A, jaw member 120 includes a series of stopmembers 90 disposed on the inner facing surface of the electricallyconductive sealing surface 122 to facilitate gripping and manipulationof tissue and to define a gap “G” (FIG. 10B) between opposing jawmembers 110 and 120 during sealing and cutting of tissue. It isenvisioned that the series of stop members 90 may be employed on one orboth jaw members 110 and 120 depending upon a particular purpose or toachieve a desired result. A detailed discussion of these and otherenvisioned stop members 90 as well as various manufacturing andassembling processes for attaching and/or affixing the stop members 90to the electrically conductive sealing surfaces 112, 122 are describedin commonly-assigned, co-pending U.S. Application Serial No.PCT/US01/11413 entitled “VESSEL SEALER AND DIVIDER WITH NON-CONDUCTIVESTOP MEMBERS” by Dycus et al. which is hereby incorporated by referencein its entirety herein.

Jaw member 120 is connected to a second electrical lead 325 b extendingfrom circuit board 170 or generator 500 (See FIG. 16) which terminateswithin the outer insulator 124 and is designed to electro-mechanicallycouple to the sealing plate 122 by virtue of a crimp-like connection 326b. As explained in more detail below, leads 325 a and 325 b allow a userto selectively supply either bipolar or monopolar electrosurgical energyto the jaw members 110 and 120 as needed during surgery.

Jaw members 110 and 120 are electrically isolated from one another suchthat electrosurgical energy can be effectively transferred through thetissue to form a tissue seal. For example and as best illustrated inFIGS. 15A and 15B, each jaw member, e.g., 110, includes auniquely-designed electrosurgical cable path disposed therethrough whichtransmits electrosurgical energy to the electrically conductive sealingsurface 112. Cable lead 325 a is held loosely but securely along thecable path to permit rotation of the jaw members 110 and 120. As can beappreciated, this isolates electrically conductive sealing surface 112from the remaining operative components of the end effector assembly100, jaw member 120 and shaft 12. The two electrical potentials areisolated from one another by virtue of the insulative sheathingsurrounding the cable leads 325 a and 325 b.

As mentioned above, jaw members 110 and 120 are engaged to the end ofrotating shaft 18 by pivot pin 185 such that rotation the rotatingassembly 80 correspondingly rotates shaft 18 (along with sleeve 17 andknife drive rod 71) which, in turn, rotates end effector assembly 100(See FIG. 12). More particularly, the distal end of rotating shaft 18 isbifurcated to include ends 18 a and 18 b which define a channel thereinfor receiving jaw members 110 and 120. Pivot pin 185 secures the jawmembers 110 and 120 to ends 18 a and 18 b through aperture 186 a and 186b defined through jaw members 110 and 120, respectively. As best seen inFIGS. 13 and 17, rotating shaft 18 is dimensioned to slidingly receiveknife drive rod 71, knife 190 and a knife guide 197 therein. Rotatingshaft 18, in turn, is rotatingly received within drive sleeve 17 whichas mentioned above connects to the drive assembly 60. The details withrespect to the knife assembly are explained in more detail with respectto FIGS. 5A, 5B, 6A, 6B, 7, 8A and 8B.

Rotating shaft 18 and drive shaft 17 are fixed to the rotating assembly80 by two rotating tabs which are engaged through slot 18 c in therotating shaft 18 such that rotating of the rotating membercorrespondingly rotates the rotating shaft 18. It is envisioned that thedrive shaft and the rotating shaft may be affixed to the rotatingassembly in other ways known in the art, snap-fit, friction fit, etc.

FIGS. 13 and 14 show the details of the forceps 10 and the componentfeatures thereof, namely, the housing 20, the drive assembly 60, therotating assembly 80, the knife assembly 70 and the handle assembly 30.More particularly, FIG. 13 shows the entire forceps 10 along with theabove-identified assemblies and components thereof in an explodedcondition and FIG. 14 shows an exploded view of the housing 20 and thecomponents contained therein.

Housing 20 includes housing halves 20 a and 20 b which, when mated, formhousing 20. As can be appreciated, housing 20, once formed, forms aninternal cavity 25 which houses the various assemblies identified abovewhich will enable a user to selectively manipulate, grasp, seal andsever tissue in a simple, effective, and efficient manner. Each half ofthe housing, e.g., half 20 b, includes a series of mechanicalinterfacing components, e.g., 205 which align and/or mate with acorresponding series of mechanical interfaces (not shown) to align thetwo housing halves 20 a and 20 b about the inner components andassemblies. The housing halves 20 a and 20 b may then be sonic welded orotherwise matingly engaged to secure the housing halves 20 a and 20 bonce assembled.

As mentioned above, the handle assembly 30 includes two movable handles30 a and 30 b which each cooperate with a toggle link 35 a and 35 b,respectively, to actuate the actuating or drive collar 69 of the driveassembly 60. The drive collar, in turn, reciprocates drive sleeve 17 toopen and close the jaw members 110 and 120 as described above. Movablehandles 30 a and 30 b are designed to provide a distinct lever-likemechanical advantage over conventional handle assemblies due to theunique position of the toggle links 35 a and 35 b which, when actuated,rotate along the longitudinal axis “A” to displace the actuation collar69. More particularly and as mentioned above, it is envisioned thatenhanced lever-like mechanical advantage for actuating the jaw members110 and 120 is gained by virtue of the unique position and combinationof various inter-cooperating elements such as the toggle links 35 a and35 b and the gear teeth 34 a and 34 b at the distal end of the handles30 a and 30 b which cooperate to reduce the overall user forcesnecessary to obtain and maintain the jaw members under ideal operatingpressures of about 3 kg/cm² to about 16 kg/cm².

As mentioned above, movement of the handles 30 a and 30 b from an openor spaced apart configuration to a closed position towards the housing20 forces the actuating collar 69 proximally against spring 63 which, inturn, translates drive sleeve 17 proximally to close the jaw members 110and 120. Moreover, as the handles 30 a and 30 b rotate to a closedposition, the handles 30 a and 30 b force the toggle links 35 a and 35 bto rotate along the longitudinal axis “A” beyond a parallel orientationwith longitudinal axis “A” such that upon release of the handles 30 aand 30 b from a closed position, the force of spring 63 maintains thetoggle links 35 a and 35 b in an over-extended\over-centered (i.e., pastparallel) configuration thereby locking the handles 30 a and 30 b (andtherefore the jaw members 110 and 120) relative to one another (SeeFIGS. 9A and 9B). To unlock the jaw members 110 and 120, the handles 30a and 30 b are moved away from one another (and the housing 20) toreturn the toggle links 35 a and 35 b to at least a parallel orientationwith respect to longitudinal axis “A” which unlocks and opens thehandles 30 a and 30 b and, in turn, the jaw members 110 and 120 forsubsequent grasping or re-grasping of tissue. Once the handles 30 a and30 b are opened past parallel the force of spring 63 facilitates openingof the handles 30 a and 30 b and the jaw members 110 and 120.

As mentioned above, handle 30 a also includes a locking flange 32 whichis dimensioned to prevent actuation of the knife assembly 70 when handle30 a is disposed in a spaced-apart or open configuration. Actuation ormovement of the handle 30 a towards the housing 20 disengages thelockout element 32 to allow movement of the knife assembly 70 toseparate tissue as explained in more detail below.

As best seen in FIG. 14, the drive assembly includes drive collar 69,spring 63 and locking sleeve 62. Toggle links 35 a and 35 b operativelyconnect the drive collar 69 to the handles 30 a and 30 b, respectively.The locking sleeve 62 is dimensioned to fit through an opening 67defined through the drive collar 69 and the spring 63 is dimensioned tofit over the locking sleeve 62. The spring 63, in turn, is biasedbetween and against the drive collar 69 and a pair of locking bolts 62 aand 62 b which to the locking sleeve 62. Upon actuation of the handles30 a and 30 b, the toggle links 35 a and 35 b force the drive collar 69proximally to compress the spring 63 against the locking bolts 62 a and62 b.

As best seen in FIGS. 9A and 9B, the locking sleeve 62 and sleeve 17 areclamped or welded together at assembly. Locking sleeve 62 includes adistal collar 62′ which abuts drive collar 69 to ensure axialtranslation of the driving collar 69 upon actuation of the handles 30 aand 30 b. Locking sleeve 62 and sleeve 17 are also dimensioned toreciprocate through locking nuts 62 a and 62 b during actuation ofhandles 30 a and 30 b which enables the spring 63 to compress againstlocking nuts 62 a and 62 b which as mentioned above, facilitates lockingthe forceps 10 in a closed orientation within desired force ranges andfacilitates opening of the handles 30 a and 30 b after activation of theforceps 10.

FIG. 14 also shows the rotating assembly 80 which includes two C-shapedrotating halves 81 a and 81 b which, when assembled about shaft 17, forma generally circular rotating member 81. More particularly, eachrotating half, e.g., 81 b, includes a series of mechanical interfaces 83which matingly engage a corresponding series of mechanical interfaces(not shown) in half 81 a to form rotating member 81. Half 81 b alsoincludes a tab or protrusion (Not shown) which together with acorresponding tab or protrusion (not shown) disposed on half 81 acooperate to matingly engage slots 17 c and 18 c on the drive shaft 17and rotating shaft 18, respectively. As can be appreciated, this permitsselective rotation of the end effector assembly 100 about axis “A” bymanipulating the rotating member 80 in the direction of the arrow “R”(see FIGS. 1A and 12).

As mentioned above, the jaw members 110 and 120 may be opened, closedand rotated to manipulate tissue until sealing is desired. This enablesthe user to position and re-position the forceps 10 prior to activationand sealing. It is envisioned that the unique feed path of the cableleads 325 a and 325 b through the rotating assembly 80, along shaft 18and, ultimately, to jaw members 110 and 120 enables the user to rotatethe end effector assembly 100 about 170 degrees in both the clockwiseand counterclockwise direction without tangling or causing undue strainon cable leads 325 a and 325 b.

As best shown in FIGS. 5A, 5B, 6A, 6B, 7, 11A, 11B and 14, the knifeassembly 70 mounts atop housing 20 and is configured to selectivelytranslate a knife bar 71 which, in turn, translates knife 190 throughtissue. More particularly, the knife assembly 70 includes a fingeractuator 76 having an elongated support base 72 affixed thereto which isselectively moveable parallel to longitudinal axis “A”. Elongatedsupport base 72 includes a proximal end which is configured as a gearrack having a series of gear teeth 72 a which depend downwardlytherefrom. Gear teeth 72 a are configured to mesh with a correspondingpinion gear 77 mounted for rotation on the housing 20. The pinion gear77 also meshes with a second gear track 75 having a plurality of gearteeth 75 a disposed on a collar 74 which is slidingly translatable atopsleeve 17. As best shown in FIGS. 9A, 9B and 11A, a pin 78 attaches thecollar 74 to a proximal end 71 b of knife bar 71 through slot 17 ddefined through sleeve 17. Proximal translation of the finger actuator76 in the direction “F” rotates the pinion gear 77 in a clockwisedirection which, in turn, forces the second gear track 75 a distally inthe direction “H” (see FIG. 7). A spring 79 biases the collar 74 againstthe housing 20 to automatically return the knife assembly 70 to apre-firing position after the finger actuator 76 is released.

The knife assembly may be configure to include a mechanical fuse toprevent excessive actuation of the knife assembly. For example, piniongear 77 may be configured to include one or more frangible or break-awayelements to prevent over extension of the finger actuator in theproximal direction. As can be appreciated, configuring the pinion gear77 in this fashion will prevent the user from overloading and damagingthe delicate knife blade 190 disposed between the jaw members 110 and120. In one embodiment, the axle of the pinion gear 77 will fracturewhen an excessive force of about 9 lbf or greater is applied in thedirection “F” (as shown in FIG. 7). In this instance and upon fractureof the pinion axle, the spring 79 automatically returns the knife blade190 to a retracted position to allow the separation of the jaw members110 and 120 which allows the forceps 10 to be safely removed from thebody without damaging tissue. As can be appreciated, the fracture of thepinion axle does not contaminate the surgical field and the fracturedgear 77 remains within the housing 20 of the forceps 10. In addition, itis envisioned that the internal operating components of the housing 20may be accessible in this instance to allow replacement of the piniongear.

It is also contemplated that other elements may be configured in asimilar fashion to limit overloading of the instrument and damagingdelicate parts associated with the forceps 10. For example, the teeth 72a on the rack could be dimensioned to fracture upon excessive force orthe track 75 a may fracture as well. Moreover, the handles 30 a and 30 bmay be equipped with a similar overloading safety mechanism whichprevents over compression of the handles 30 a and 30 b and the driveassembly 60 or handle assembly 30. For example, links 35 a and 35 b maybe configured to fracture upon an overloading condition or drive collar69.

As mentioned above, the knife assembly 70 is prevented from beingactuated when the jaw members 110 and 120 are opened by virtue of flange32 disposed on handle 30 a being positioned to prevent distal activationof the collar 74 when handles 30 a and 30 b are opened. Upon movement ofthe handles 30 a and 30 b to a closed position, the flange 32 ispositioned to allow distal translation of collar 74 to actuate the knifebar 71.

The operating features and relative movements of the internal workingcomponents of the forceps 10 are shown by phantom representation in thevarious figures. As the handles 30 a and 30 b are squeezed, the drivecollar 69, through the mechanical advantage of the in-line toggle links35 a and 35 b, is moved proximally which, in turn, compresses a spring63 against the locking nuts 62 a and 62 b. As a result thereof, thedrive collar 69 reciprocates locking sleeve 62 proximally which, inturn, reciprocates drive sleeve 17 proximally to closes jaw members 110and 120. Once the jaw members 110 and 120 are closed about tissue theuser can selectively energize the electrically conductive sealing platesfor either monopolar activation or bipolar activation to treat tissue.

As best shown in FIGS. 6A, 14 and 16, the forceps 10 includes twoswitches 250 and 260 which are mounted within or atop the housing 20 andwhich allow a user to selectively activate the forceps 10 to selectivelytransmit bipolar energy to the jaw members 110 and 120 or selectivelytransmit monopolar energy to the jaw members 110 and 120 or to a singlejaw member, e.g., jaw member 110. For the purposes herein, it isenvisioned that either switch, e.g., switch 250, may be configured formonopolar activation and the other switch, e.g., switch 260, may beconfigured for bipolar activation. Further the switches 250 and 260 mayinclude indicia or other identifying elements, e.g., raisedprotuberances, scallops, different shapes, etc., to distinguish the twoswitches 250 and 260 from one another which may prove especially usefulduring wet operating conditions.

In one particularly useful embodiment and as best shown in FIG. 6A,switches 250 and 260 are mounted within the housing 20 on opposite sidesof longitudinal axis “A” and on opposite sides of the knife assembly 70.As can be appreciated, the knife assembly 70 (and actuation thereof) andthe switches 250 and 260 (and the activation thereof) are convenientlylocated to facilitate actuation/activation by the user during operatingconditions. For example, it is contemplated that the user may utilizethe same finger to both activate the switches 250 and 260 to treattissue and actuate the knife assembly 70 to cut tissue once treated.

As shown in FIGS. 6A and 16, cable 310 is fed through the housing 20 bon one side of the drive assembly 60 and electromechanically connects toa printed circuit board 172 of the switch assembly 170. Moreparticularly, cable 310 is internally divided into a plurality of leads311 a-311 f which are secured by a crimp-like connector 174 to a seriesof corresponding contacts 176 a-176 f extending from the printed circuitboard 172 or to other electrically conductive leads which ultimatelyconnect to the jaw members. Other electromechanical connections are alsoenvisioned which are commonly known in the art, e.g., IDC connections,soldering, etc. It is envisioned the various leads 311 a-311 f areconfigured to transmit different electrical potentials or controlsignals to the printed circuit board 172 which, in conjunction withgenerator 500, regulates, monitors and controls the electrical energy tothe jaw members 110 and 120. As mentioned above with respect to thedescription of the jaw members, electrical leads 325 a and 325 b extendthrough the rotating member 80, along shaft 18 to ultimately connect tothe jaw members 110 and 120.

FIG. 23 shows a schematic representation of a control circuit 510 foruse with the presently disclosed forceps 10. As mentioned above, forceps10 is configured to operate in two independent modes ofoperation—bipolar mode and monopolar mode for different surgicalprocedures. When one of the switches 250 (S1 in FIGS. 19 and 23) or 260(S2 in FIGS. 19 and 23) of switch assembly 170 is depressed, a contact(not shown) on the switches 250 and 260 activates the appropriateelectrical potential (or potentials) to the jaw members 110 and 120which is (are) carried through leads 325 a and/or 325 b. For example, ifswitch 250 (LigaSure™ activation) is depressed, the circuit board 172signals the generator 500 to configures the forceps 10 as a bipolarforceps and lead 325 a carries a first electrical potential to jawmember 110 and lead 325 b carries a second electrical potential to jawmember 120. As such the jaw members 110 and 120 conduct bipolar energythrough the tissue upon activation to create a tissue seal. FIG. 23shows one example of contemplated electrical circuitry which may beutilized to accomplish this purpose.

If switch 260 (monopolar activation) is depressed, the circuit board 172configures the forceps as a monopolar forceps and lead 325 a caries afirst electrical potential to jaw member 110 to coagulate or otherwisetreat tissue in a monopolar fashion. As mentioned above, jaw member 110includes a monopolar extension which facilitates monopolar treatment ofvarious tissue types, e.g., avascular tissue structures, and/or allowsquick dissection of narrow tissue planes. Activation of the monopolarextension may be controlled by an activation circuit which allows theuser to selectively apply monopolar energy or bipolar energy as neededduring surgery. One envisioned activation circuit is disclosed incommonly-owned U.S. patent application Ser. No. 10/970,307 entitled“BIPOLAR FORCEPS HAVING MONOPOLAR EXTENSION” and U.S. application Ser.No. 10/988,950 entitled “BIPOLAR FORCEPS HAVING MONOPOLAR EXTENSION”,the entire contents of both of these applications being herebyincorporated by reference herein.

Alternatively and as best shown in FIG. 23, during the monopolar modewhen switch 260 is depressed, the generator (or the printed circuitboard) can direct both leads 325 a and 325 b to carry the sameelectrical potential to jaw members 110 and 120 depending upon aparticular purpose or depending upon a desired surgical treatment, e.g.,so-called “coagulative painting”. As can be appreciated, in a monopolarmode, a return pad would be necessarily placed in contact with thepatient to act as a return path (not shown) for the electrical energy.The return pad in this instance would connect to the generator 500directly or though a return pad control mechanism (not shown) which maybe configured to monitor certain parameters of the return pad. Variousenvisioned control systems are disclosed in commonly-owned U.S. patentapplication Ser. No. 10/918,984 entitled “MULTIPLE RF RETURN CABLE PADCONTACT DETECTION SYSTEM”, U.S. patent application Ser. No. 09/310,059entitled “ELECTROSURGICAL RETURN ELECTRODE MONITOR” (now U.S. Pat. No.6,258,085), U.S. Provisional Patent Application Ser. No. 60/616,970entitled “DEVICE FOR DETECTING HEATING UNDER A PATIENT RETURN ELECTRODE”and U.S. Provisional Patent Application Ser. No. 60/666,798 entitled“TEMPERATURE REGULATING PATIENT RETURN ELECTRODE AND RETURN ELECTRODEMONITORING SYSTEM”, the entire contents of all of which are incorporatedby reference wherein.

In a bipolar mode, the circuit 510 (schematically-illustrated in FIG.23) electrical routes energy to the two jaw members 110 and 120. Moreparticularly, when switch 250 is depressed an isolated circuit 520 ofthe circuit 510 recognizes a resistance drop thereacross which isrecognized by the generator to initiate electrosurgical energy to supplya first electrical potential to jaw member 110 and a second electricalpotential to jaw member 120. Switch 520 acts as an insolated controlcircuit and is protected by circuitry within the generator from thehigher current loop which supplies electrical energy to the jaw members110 and 120. This reduces the chances of electrical failure of theswitch 260 due to high current loads during activation.

As best shown in FIG. 14, handle 30 a also includes a switch lockoutmechanism 255 which may be configured to prevent activation of one orboth switches 250 and 260 when the jaw members 110 and 120 are disposedin an open configuration. More particularly, lockout mechanism 255extends from handle 30 a towards housing 20 and is selectively moveablewith the handle 30 a from a first position wherein the lockout mechanism255 prevents one or both switches 250 and 260 from being depressed tocontact the circuit board 172 to a second position closer to the housing20 wherein the lockout mechanism 255 is positioned to allow activationof switch 250 (or switches 250 and 260). It is envisioned that thelockout mechanism 255 may be configured as a purely mechanical lockoutwhich physically prevents movement of one or both switches 250 and/or260 or may be configured as an electromechanical lockout which includesa mechanical element which activates a safety switch to allowactivation. Moreover, the switch lockout mechanism 255 may be configuredsuch that one or both switches may be independently and exclusivelyactivatable, i.e., only one switch may be activated at a time.

For example, flex circuit 170 may include a safety switch 171 which isactivated when lockout mechanism 255 physically engages safety switch171 to close the circuit to permit electrosurgical activation. In otherwords, the safety switch 171 is deflected or physically engaged (i.e.,by virtue of the movement of lockout mechanism 255 when the handles 30 aand 30 b are closed) to close the electrical path and permitelectrosurgical activation. Further details with respect to variousembodiments of the safety switch are described below with respect toFIGS. 18-21D. It is also envisioned that a purely electrical safetyswitch (See FIG. 23) may be included which allows activation based uponthe satisfaction of an electrical condition, e.g., optical alignment ofpoints on the handle 30 a (or handles (30 a and 30 b), magnetic orelectromagnetic alignment (or misalignment) to close a switch, proximitysensors, scanners, mercury (or the like) switches, etc. Again, thesafety switch 171 may be configured such that one or both switches 250and/or 260 may be independently and exclusively activatable, i.e., onlyone switch may be activated at a time.

As can be appreciated, locating the switches 250 and 260 on the housing20 is advantageous during operating conditions since this positioningreduces the amount of electrical cable in the operating room andeliminates the possibility of activating the wrong instrument or wrongswitch during a surgical procedure due to “line-of-sight” activation. Anautomatic safety circuit or an electromechanical or mechanical safetylock (not shown) may be employed which prevents the switches 250 and 260from energizing the jaw members 110 and 120 in a different mode (i.e.bipolar or monopolar mode) without de-activating a safety circuit orother safety mechanism, i.e., independent and exclusive activation. Forexample, it may be desirable to configure the switch assembly 70 suchthat it must be re-set before switching between electrical modes.Re-setting may be accomplished by re-grasping tissue, re-opening thehandles 30 a and 30 b, a reset switch or re-set lever, or other wayscustomary in the art.

As can be appreciated various switching algorithms (See FIG. 23) may beemployed to activate both the bipolar mode for vessel sealing and themonopolar mode for additional tissue treatments (e.g., coagulation,dissection, etc.). It is also envisioned that the safety or lockoutmentioned above may be employed as part of an algorithm to eitherelectrically, mechanically or electromechanically “lock out” oneelectrical mode during activation of the other electrical mode. Inaddition, it is contemplated that a toggle switch (or the like) may beemployed to activate one mode at a time for safety reasons.

The safety switch 171 when assembled (and when the handles 30 a′ and 30b and jaws 110 and 120 are opened) is secured against an interior wallor ledge 173 of housing 20 b as shown in FIG. 22A. Upon movement of thehandle 30 a toward housing 20 b, safety lockout 255 moves inwardlyrelative to the housing 20 b toward the safety switch 171 as shown inFIG. 22B. As the handles 30 a and 30 b move toward the closed position(as described in detail above), the safety lockout 255 engages thesafety circuit 171′ (S3 in FIGS. 19 and 23) to complete circuit andallow selective activation of the forceps 10 (see also FIG. 23).

As best shown in FIGS. 14 and 23-27, the switching assembly may includean intensity control 150 which electromechanically connects to thecircuit board 172 and which is configured to allow the user toselectively regulate the intensity of the electrosurgical energy duringoperating conditions. It is envisioned that the intensity control 150 isparticularly configured to regulate the intensity control when theforceps is configured in a monopolar mode. In one particularly usefulembodiment, intensity control 150 is elongated and includes a contact154 which extends transversally therefrom to electro-mechanicallyinterface with the circuit board 172 through the housing 20. Anactuating knob 151 extends transversally from the opposite side of theintensity control 150 and is dimensioned to protrude from the side ofhousing 20 when assembled (see FIGS. 5A, 5B, 6A and 6B). In oneparticularly useful embodiment, intensity control 150 is configured toslide along housing 20 to regulate the intensity level as desired.

It is envisioned that the intensity control 150 may be configured toslide along the housing 20 in a discreet or continuous manner dependingupon a particular purpose. For example and as best shown in FIGS. 24-27,one envisioned intensity control 150′ may be dimensioned to include anactuating knob 151′ which extends transversally from one side of theintensity control 150′ to protrude from housing 20 when assembled. Acantilevered extension 153′ having a detent 155′ at an end thereofextends generally perpendicularly to the intensity control 150′ and iscentrally disposed in the intensity control 150′. The detent 155′ of thecantilevered extension 153′ is dimensioned to engage a correspondingmechanical interface or track 161′ disposed within the housing 20 (SeeFIG. 26). As can be appreciated mechanical advantage is created by thecantilevered extension 153′ to facilitate actuation of the detent 155′within the housing 20.

The detent 155′ is selectively moveable (by selectively actuating theintensity knob 150′) to engage various recesses 163 a′, 163 b′, 163 c′,163 d′ and 163 e′ disposed in the track 161′ to lock the intensitycontrol knob 150′ at a discreet intensity setting as desired for aparticular surgical purpose. It is envisioned that the track 161′ mayinclude one or more larger recesses, e.g., recess 163 c′, to facilitatereturning the intensity control 150′ to a central (as shown),proximal-most or distal-most position.

The opposing end of the intensity control 150′ opposite detent 155′includes a slider bump or other mechanical interface 167′ which isoperatively engaged atop the flexible circuit board 170 and 170′. Theslide bump 167′ is configured to deflect the flexible circuit board 170(or 170′) at varying positions as the intensity control 150′ is moved.Deflecting the circuit board 170 (or 170′) at different locationsadjusts the intensity settings by controlling the impedance of theflexible printed circuit 170 or 170′ as described below. In other words,the slide bump 167′ creates enough depression force to switch theflexible circuit 170 to a different control setting. The switch occurswhen one conductive layer on the flexible circuit board 170 flexes totouch another conductive layer to create an electrical connection. Ascan be appreciated this allows the user to selectively regulate theintensity of the electrosurgical energy during operating conditions. Asshown, the forceps 10 includes five (5) different intensity settings.

As best shown in FIG. 27, the intensity control 150′ may be positionedatop a railway 169′ defined with the housing 20. The railway 169′ isconfigured to facilitate translational movement of the intensity control150′ from a proximal-most position to a distal-most position atop theflexible circuit 170 (or 170′) and within the various recesses 163a′-163 e′.

Various types of indicia 155 and/or tactile feedback elements (notshown) may be utilized to denote the position and/or intensity level ofthe electrical energy, e.g., numbers, graphical indicia, mechanicalinterfaces, etc. It is also envisioned that the user may configure theinitial intensity level on the generator 500 (See FIG. 16) and theintensity control 150 on the forceps 10 may be utilized to increase ordecrease the pre-set level by a certain percentage by moving knob 151.

Intensity controller 150 may be configured to function as a slidepotentiometer, sliding over and along the flexible or printed circuitboard (which may be configured to function as a voltage divider networkor “VDN”). For example, the intensity controller 150 may be configuredto have a first position wherein knob 151 is disposed at a proximal-mostposition (e.g., closest to the user) which corresponds to a relative lowintensity setting, a second position wherein knob 151 is disposed at adistal-most position (e.g., furthest from the user) corresponding to arelative high intensity setting, and a plurality of intermediatepositions wherein knob 151 is disposed at varying positions therebetweencorresponding to various intermediate intensity settings. As can beappreciated, the intensity settings from the proximal end to the distalend may be reversed, e.g., high to low. One embodiment of an intensitycontroller 150 is disclosed in commonly-owned U.S. patent Ser. No.11/337,990 entitled “ELECTROSURGICAL PENCIL WITH ADVANCED ES CONTROLS”,the entire contents of which being incorporated by reference herein.

As illustrated in FIG. 14 and as mentioned above, knob 151 may bedimensioned to ride along a guide channel 157 disposed within housing 20a which is provided with a series of discreet or detented positionsdefining a series of positions, e.g., five, to allow easy selection ofthe output intensity from the low intensity setting to the highintensity setting. The series of cooperating discreet or detentedpositions also provide the surgeon with a degree of tactile feedback.Accordingly, in use, as intensity controller 150 slides distally andproximally, a mechanical interface 158 disposed atop contact 154selectively engages a series of corresponding detents (not shown) to setthe intensity level as well as to provide the user with tactile feedbackas to when the intensity controller 150 has been set to the desiredintensity setting. Alternatively, audible feedback can be produced fromintensity controller 150 (e.g., a “click”), from electrosurgical energysource 500 (e.g., a “tone”) and/or from an auxiliary sound-producingdevice such as a buzzer (not shown).

Intensity controller 150 may also be configured and adapted to adjustthe power parameters (e.g., voltage, power and/or current intensity)and/or the power verses impedance curve shape to affect the perceivedoutput intensity. For example, the greater intensity controller 150 isdisplaced in a distal direction the greater the level of the powerparameters transmitted to the jaw members 110 and 120 (or simply jawmember 110 when disposed in a monopolar configuration). When the forcepsis disposed in a monopolar mode, current intensities can range fromabout 60 mA to about 240 mA with tissue having an impedance of about 2 kohms. An intensity level of 60 mA may provide very light and/or minimalcutting/dissecting/hemostatic effects. An intensity level of 240 mAprovides very aggressive cutting/dissecting/hemostatic effects.

Intensity settings are typically preset and selected from a look-uptable based on a desired surgical effect, surgical specialty and/orsurgeon preference. The selection may be made automatically or selectedmanually by the user.

It is envisioned that when the forceps 10 is changed from one mode toanother mode, the intensity controller 150 may be configured such thatit must be reset (e.g., the knob 151 is re-positioned to theproximal-most end of guide channels 157 thus re-setting the intensitylevel to the preset configuration. After being reset, intensitycontroller 150 may be adjusted as needed to the desired and/or necessaryintensity level for the mode selected.

It is envisioned and contemplated that the circuit board 172 orgenerator 500 may also include an algorithm which stores the lastintensity level setting for each mode. In this manner, intensitycontroller 150 does not have to be reset to the last operative valuewhen the particular mode is re-selected.

The present disclosure also relates to a method for treating tissue withelectrosurgical energy from the electrosurgical generator 500 whichincludes the steps of: providing an endoscopic forceps 10 including ahousing 20 having a shaft 12 affixed thereto. The shaft 12 includesfirst and second jaw members, 110 and 120, respectively, attachedproximate a distal end of the shaft 12. An actuator or handle assembly30 is included for moving jaw members 110 and 120 relative to oneanother from a first position wherein the jaw members 110 and 120 aredisposed in spaced relation relative to one another to a second positionwherein the jaw members 110 and 120 cooperate to grasp tissuetherebetween. The switch assembly 170 is included on the housing 20which permits the user to selectively energize the jaw members 110 and120 in a monopolar or bipolar mode to treat tissue.

As can be appreciated and as mentioned above, the switch assembly 170includes switches 250 and 260, printed circuit board 172 and connectors176 a-d. An intensity control 150 may also be included with the switchassembly 170 to regulate the intensity level of the electrosurgicalenergy when disposed in either mode. In this particular method, thesteps further include: grasping tissue between the jaw members 110 and120; selectively activating the jaw members 110 and 120 to treat tissuedisposed between the jaw members 110 and 120 in a bipolar or monopolarfashion; and selectively regulating the intensity of the electrosurgicalenergy by controlling the intensity control 150.

Other steps of the method may include the steps of: providing a knifeassembly 70 which is configured for selective actuation of a knife andthe step of selectively actuating the knife assembly 70 to advance theknife 190 to divide tissue after tissue treatment. Still other steps mayinclude: adjusting the intensity of the electrosurgical energy as neededduring operating conditions; unlocking the knife assembly 70 prior toactuation or unlocking the knife assembly 70 simultaneously whenactuating the handles 30 a and 30 b from the first and second positions.

As best shown in FIG. 17, the distal end 71 a of the elongated knife bar71 of the knife assembly 70 attaches to the knife 190 at a proximal endthereof. It is envisioned that the knife 190 may be attached to theknife bar 71 in any way known in the art, e.g., snap-fit, fiction-fit,pinned, welded, glued, etc. In the particular embodiment shown in FIG.17, a clamp collar 197 is used to retain the knife 190 securely engagedwith the knife bar 71.

Switches 250 and 260 are typically push-button-type and ergonomicallydimensioned to seat within respective apertures 250′ and 260′ of housing20 (once assembled). It is envisioned that the switches 250 and 260permit the user to selectively activate the forceps 10 for surgicaltreatment of tissue. More particularly, when either switch 250 or 260 isdepressed, electrosurgical energy is transferred through leads 325 aand/or 325 b to respective jaw members 110 and 120.

Again and as noted above, a safety switch 255 (or circuit or algorithm(not shown)) may be employed such that one or both of the switches 250and 260 cannot fire unless the jaw members 110 and 120 are closed and/orunless the jaw members 110 and 120 have tissue held therebetween. In thelatter instance, a sensor (not shown) may be employed to determine iftissue is grasped between jaw members. In addition, other sensormechanisms may be employed which determine pre-surgical, concurrentsurgical (i.e., during surgery) and/or post surgical conditions. Thesesensor mechanisms may also be utilized with a closed-loop feedbacksystem coupled to the electrosurgical generator to regulate theelectrosurgical energy based upon one or more pre-surgical, concurrentsurgical or post surgical conditions. Various sensor mechanisms andfeedback systems are described in commonly-owned, co-pending U.S. patentapplication Ser. No. 10/427,832 entitled “METHOD AND SYSTEM FORCONTROLLING OUTPUT OF RF MEDICAL GENERATOR”, the entire contents ofwhich being hereby incorporated by reference herein.

Turning back to FIG. 14 which shows the exploded view of the housing 20,rotating assembly 80, drive assembly 70, handle assembly 30 and switchassembly 170, it is envisioned that all of these various component partsalong with the shaft 12 and the end effector assembly 100 are assembledduring the manufacturing process to form a partially and/or fullydisposable forceps 10. For example and as mentioned above, the shaft 12and/or end effector assembly 100 may be disposable and, therefore,selectively/releasably engagable with the housing 20 and rotatingassembly 80 to form a partially disposable forceps 10 and/or the entireforceps 10 may be disposable after use.

It is envisioned that the opposing jaw members 110 and 120 may berotated and partially opened and closed without unlocking the knifeassembly 70 which, as can be appreciated, allows the user to grip andmanipulate the tissue without premature activation of the knife 190. Asmentioned below, only a substantially fully closed position of thehandles 30 a and 30 b will unlock the knife assembly 70 for actuation.

Once the desired position for the sealing site is determined and the jawmembers 110 and 120 are properly positioned, handles 30 a and 30 b maybe squeezed to actuate the drive assembly 60 to close the jaw members110 and 120 about tissue. As mentioned above, when the handles 30 a and30 b are fully closed about tissue the toggle links 35 a and 35 bover-rotate past parallel with the longitudinal axis “A” such thatslightly releasing the handles 30 a and 30 b biases the spring 63 tolock the handles 30 a and 30 b relative to one another. As can beappreciated, when the handles 30 a and 30 b lock relative to oneanother, the jaw members 110 and 120, in turn, lock and secure abouttissue within a pressure range of about 3 kg/cm² to about 16 kg/cm² and,preferably, with a pressure range of about 7 kg/cm² to about 13 kg/cm².The forceps 10 is now ready for selective application of electrosurgicalenergy and subsequent separation of the tissue (if desired).

It is envisioned that the combination of the mechanical advantage gainedby the disposition of the toggle links 35 a and 35 b relative to thelongitudinal axis “A” along with the mechanical advantage gained byconfiguring the distal ends 34 a′ and 34 b′ as inter-engaging gear teethwill facilitate and assure consistent, uniform and accurate closurepressure about the tissue within the desired working pressure range ofabout 3 kg/cm² to about 16 kg/cm² and, in one particularly usefulembodiment, about 7 kg/cm² to about 13 kg/cm². By controlling theintensity, frequency and duration of the electrosurgical energy appliedto the tissue, the user can either cauterize, coagulate/desiccate, sealand/or simply reduce or slow bleeding by activating either or bothswitches 250 and 260.

In one or more particularly useful embodiments, the electricallyconductive sealing surfaces 112, 122 of the jaw members 110, 120,respectively, are relatively flat to avoid current concentrations atsharp edges and to avoid arcing between high points. In addition and dueto the reaction force of the tissue when engaged, jaw members 110 and120 are preferably manufactured to resist bending. For example, the jawmembers 110 and 120 may be tapered along the width thereof which isadvantageous since the thicker proximal portion of the jaw members 110and 120 will resist bending due to the reaction force of the tissue.

As mentioned above, at least one jaw member, e.g., 120, may include oneor more stop members 90 which limit the movement of the two opposing jawmembers 110 and 120 relative to one another. The stop member(s) 90 maybe dimensioned to extend from the sealing surface 122 a predetermineddistance according to the specific material properties (e.g.,compressive strength, thermal expansion, etc.) to yield a consistent andaccurate gap distance “G” during sealing. The gap distance betweenopposing sealing surfaces 112 and 122 during sealing ranges from about0.001 inches to about 0.006 inches and, in one particularly usefulembodiment, between about 0.002 and about 0.003 inches. Thenon-conductive stop member(s) 90 may be molded onto the jaw members 110and 120 (e.g., overmolding, injection molding, etc.), stamped onto thejaw members 110 and 120 or deposited (e.g., deposition) onto the jawmembers 110 and 120. For example, one technique involves thermallyspraying a ceramic material (or the like) onto the surfaces of one orboth jaw members 110 and 120 to form the stop member(s) 90. Severalthermal spraying techniques are contemplated which involve depositing abroad range of heat resistant and insulative materials on varioussurfaces to create stop members 90 for controlling the gap distancebetween electrically conductive surfaces 112 and 122.

As energy is being selectively transferred to the end effector assembly100, across the jaw members 110 and 120 and through the tissue, a tissueseal forms isolating two tissue halves. At this point and with otherknown vessel sealing instruments, the user must remove and replace theforceps 10 with a cutting instrument (not shown) to divide the tissuehalves along the tissue seal. As can be appreciated, this is both timeconsuming and tedious and may result in inaccurate tissue divisionacross the tissue seal due to misalignment or misplacement of thecutting instrument along the ideal tissue cutting plane.

As explained in detail above, the present disclosure incorporates knifeassembly 70 which, when activated via the trigger knob 76, progressivelyand selectively divides the tissue along an ideal tissue plane inprecise manner to effectively and reliably divide the tissue into twosealed halves with a tissue gap therebetween. The knife assembly 70allows the user to quickly separate the tissue immediately after sealingwithout substituting a cutting instrument through a cannula or trocarport. As can be appreciated, accurate sealing and dividing of tissue isaccomplished with the same forceps 10.

It is envisioned that knife blade 190 may also be coupled to the same oran alternative electrosurgical energy source to facilitate separation ofthe tissue along the tissue seal. Moreover, it is envisioned that theangle of the knife blade tip 192 may be dimensioned to provide more orless aggressive cutting angles depending upon a particular purpose. Forexample, the knife blade tip 192 may be positioned at an angle whichreduces “tissue wisps” associated with cutting. More over, the knifeblade tip 192 may be designed having different blade geometries such asserrated, notched, perforated, hollow, concave, convex etc. dependingupon a particular purpose or to achieve a particular result. It is alsocontemplated that the forceps 10 may be activated in a monopolar mode todivide tissue after formation of a tissue seal.

Once the tissue is divided into tissue halves, the jaw members 110 and120 may be opened by re-grasping the handles 30 a and 30 b moving eachhandle 30 a and 30 b outwardly relative to the housing 20. It isenvisioned that the knife assembly 70 generally cuts in a progressive,unidirectional fashion (i.e., distally).

As best shown in FIGS. 3A-3C, the proximal portions of the jaw members110 and 120 and the distal end 16 of shaft 12 may be covered by aresilient or flexible insulating material or boot 220 to reduce straycurrent concentrations during electrosurgical activation especially inthe monopolar activation mode. More particularly, the boot 220 isflexible from a first configuration (See FIG. 3B) when the jaw members110 and 120 are disposed in a closed orientation to a second expandedconfiguration (See FIGS. 3A and 3C) when the jaw members 110 and 120 areopened. As can be appreciated, when the jaw members 110 and 120 open,the boot flexes or expands at areas 220 a and 220 b to accommodate themovement of the proximal flanges 113 and 123. Further details relatingto one envisioned insulating boot 220 are described with respect tocommonly-owned and concurrently-filed U.S. Application ProvisionalApplication Ser. No. 60/722,213 entitled “INSULATING BOOT FORELECTROSURGICAL FORCEPS”, the entire contents of which beingincorporated by reference herein.

FIGS. 18-22C show one particularly useful embodiment of a safety lockoutmechanism 255′ for use with a flex circuit 170′. Much like the abovedescribed safety lockout 255, lockout mechanism 255′ is disposed onhandle 30 a′ at a point distal to trigger lockout 32′. This particularsafety lockout 255′ is configured to extend normally to the longitudinalaxis “A” as shown best in FIG. 18. Movement of handle 30 a′ towardshousing 20 causes the safety lockout 255′ to move towards the housing 20in a similar manner as described above. Safety lockout 255′ isconfigured to engage a safety switch 171′ of the flex circuit 170′ toallow activation only when handle 30 a′ (and, in turn, jaw members 110and 120) is moved relative to housing 20 (i.e., both handles 30 a′ and30 b are closed to grasp tissue).

As best shown in schematic illustration of FIG. 20, safety switch 171′is designed as part of a circuit 400 such that circuit 400 remains openuntil the safety switch 171′ is activated. FIG. 21 shows the position ofsafety switch 171′ prior to and after assembly. More particularly, uponassembly, the safety switch 171′ is flexed into position (see phantomrepresentation) by the top portion 20 a of housing 20 such that thedistal portion of the safety switch 171′ is biased and wedged against aninterior wall or ledge 173′ disposed within housing 20 b. It isenvisioned that the safety switch 171′ will remain secured in place forthe useful life of the forceps 10.

FIGS. 22A-22C show the activation sequence of the safety switch 171′.More particularly and as mentioned above, the safety switch 171′ whenassembled (and when the handles 30 a′ and 30 b and jaws 110 and 120 areopened) is secured against an interior wall or ledge 173′ of housing 20b as shown in FIG. 22A. Upon movement of the handle 30 a′ toward housing20 b, safety lockout 255′ moves inwardly relative to the housing 20 btoward the safety switch 171′ as shown in FIG. 22B. As the handles 30 a′and 30 b move toward the closed position (as described in detail above),the safety lockout 255′ engages the safety circuit 171′ to completecircuit 400 and allow selective activation of the forceps 10.

It is envisioned that the safety switch 171′ may be configured to allowboth bipolar and monopolar activation once closed or configured in amore restrictive fashion, e.g., only permit one type of electricalactivation at a time without re-setting the safety switch 171′ (i.e.,opening and re-grasping the handles 30 a′ and 30 b, a separate toggleswitch (not shown), etc.). Moreover, it is also envisioned that thesafety switch 171′ may be configured to simply safeguard against theactivation of one of the modes (i.e., the monopolar mode) depending upona particular purpose and the other mode (i.e., the bipolar mode) is notrestricted by the safety switch 171′.

From the foregoing and with reference to the various figure drawings,those skilled in the art will appreciate that certain modifications canalso be made to the present disclosure without departing from the scopeof the same. For example, it may be preferable to add other features tothe forceps 10, e.g., an articulating assembly to axially displace theend effector assembly 100 relative to the elongated shaft 12.

It is also contemplated that the forceps 10 (and/or the electrosurgicalgenerator used in connection with the forceps 10) may include a sensoror feedback mechanism (not shown) which automatically selects theappropriate amount of electrosurgical energy to effectively seal theparticularly-sized tissue grasped between the jaw members 110 and 120.The sensor or feedback mechanism may also measure the impedance acrossthe tissue during sealing and provide an indicator (visual and/oraudible) that an effective seal has been created between the jaw members110 and 120. Examples of such sensor systems are described incommonly-owned U.S. patent application Ser. No. 10/427,832 entitled“METHOD AND SYSTEM FOR CONTROLLING OUTPUT OF RF MEDICAL GENERATOR”, theentire contents of which being incorporated by reference herein.

Moreover, it is contemplated that the knife assembly 70 may includeother types of recoil mechanisms which are designed to accomplish thesame purpose, e.g., gas-actuated recoil, electrically-actuated recoil(i.e., solenoid), etc. It is also envisioned that the forceps 10 may beused to cut tissue without sealing. Alternatively, the knife assembly 70may be coupled to the same or alternate electrosurgical energy source tofacilitate cutting of the tissue.

Although the figures depict the forceps 10 manipulating an isolatedvessel, it is contemplated that the forceps 10 may be used withnon-isolated vessels as well. Other cutting mechanisms are alsocontemplated to cut tissue along the ideal tissue plane.

It is envisioned that the outer surface of the end effector assembly 100may include a nickel-based material, coating, stamping, metal injectionmolding which is designed to reduce adhesion between the jaw members 110and 120 with the surrounding tissue during activation and sealing.Moreover, it is also contemplated that the conductive surfaces 112 and122 of the jaw members 110 and 120 may be manufactured from one (or acombination of one or more) of the following materials: nickel-chrome,chromium nitride, MedCoat 2000 manufactured by The ElectrolizingCorporation of OHIO, inconel 600 and tin-nickel. The tissue conductivesurfaces 112 and 122 may also be coated with one or more of the abovematerials to achieve the same result, i.e., a “non-stick surface”. Ascan be appreciated, reducing the amount that the tissue “sticks” duringsealing improves the overall efficacy of the instrument.

One particular class of materials disclosed herein has demonstratedsuperior non-stick properties and, in some instances, superior sealquality. For example, nitride coatings which include, but not are notlimited to: TiN, ZrN, TiAlN, and CrN are preferred materials used fornon-stick purposes. CrN has been found to be particularly useful fornon-stick purposes due to its overall surface properties and optimalperformance. Other classes of materials have also been found to reducingoverall sticking. For example, high nickel/chrome alloys with a Ni/Crratio of approximately 5:1 have been found to significantly reducesticking in bipolar instrumentation. One particularly useful non-stickmaterial in this class is Inconel 600. Bipolar instrumentation havingsealing surfaces 112 and 122 made from or coated with Ni200, Ni201(˜100% Ni) also showed improved non-stick performance over typicalbipolar stainless steel electrodes.

While the drawings show one particular type of monopolar lockout orsafety mechanism 255 for use with the presently disclosed forceps, FIGS.18 and 19 show an alternative safety lockout mechanism which may beemployed with the forceps 10.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of preferred embodiments. Those skilled in the art willenvision other modifications within the scope and spirit of the claimsappended hereto.

1. An endoscopic forceps, comprising: a housing having a shaft attachedthereto, the shaft including a pair of jaw members disposed at a distalend thereof; a drive assembly disposed in the housing operable to movethe jaw members relative to one another from a first position, whereinthe jaw members are disposed in spaced relation relative to one another,to a second position, wherein the jaw members are closer to one another,for manipulating tissue; a pair of handles operatively connected to thedrive assembly, the handles being movable relative to the housing toactuate the drive assembly to move the jaw members; each jaw memberadapted to connect to a source of electrical energy such that the jawmembers are capable of conducting energy for treating tissue; and aknife assembly operatively associated with the housing, the knifeassembly being selectively actuatable to advance a knife through tissuedisposed between the jaw members when the jaw members are disposed inthe second position, the knife assembly including at least one safetymechanism to prevent damaging the knife upon selective actuationthereof, the safety mechanism including a mechanical fuse that fracturesupon exertion of excessive force to actuate the knife assembly.
 2. Anendoscopic forceps according to claim 1 wherein the knife assemblyincludes a pinion gear interdisposed between gear teeth and a trackwhich cooperate to advance the knife distally through the jaw members,the mechanical fuse being operatively associated with at least one ofthe pinion gear, gear teeth and track.
 3. An endoscopic forcepsaccording to claim 1 wherein the knife assembly includes a pinion gearinterdisposed between gear teeth and a track which cooperate to advancethe knife distally through the jaw members, the pinion gear including anaxle which fractures upon excessive force to actuate the knife assembly.4. An endoscopic forceps according to claim 3 wherein the excessiveforce is at least about 9 lbf.
 5. An endoscopic forceps according toclaim 1 wherein the excessive force is at least about 9 lbf.
 6. Anendoscopic forceps according to claim 1 wherein the knife assemblyincludes a pinion gear interdisposed between gear teeth and a trackwhich cooperate to advance the knife distally through the jaw members,the gear teeth being biased by a spring to return the knife assembly toan unactuated position.
 7. An endoscopic forceps according to claim 6wherein upon the exertion of excessive force, the mechanical fusefractures and the spring automatically returns the knife assembly to theunactuated position which, in turn, allows the user to move the handlesrelative to one another to release tissue.
 8. An endoscopic forcepsaccording to claim 1 further comprising: a first switch disposed on thehousing and being activatable to selectively deliver energy of a firstelectrical potential to at least one jaw member for treating tissue in amonopolar fashion; and a second switch disposed on the housing and beingactivatable to selectively deliver energy of a first electricalpotential to one jaw member and selectively deliver energy of a secondelectrical potential to the other jaw member for treating tissue in abipolar fashion.
 9. An endoscopic forceps according to claim 8 whereinthe forceps includes a monopolar lockout that prevents activation of thefirst switch when the jaw members are disposed in the first position.10. An endoscopic forceps according to claim 9 wherein the monopolarlockout includes a mechanical interface disposed on at least one of thehandles that prevents activation of the first switch when the handlesare disposed in a first position relative to the housing and permitsactivation of the first switch when the handles are disposed in a secondposition relative to the housing.
 11. An endoscopic forceps according toclaim 9 wherein the monopolar lockout includes a pressure activatedsafety switch disposed in the housing and movement of the handles from afirst position relative to the housing to a second position relative tothe housing closes the pressure activated safety switch to allowactivation of the first switch.
 12. An endoscopic forceps according toclaim 1 wherein at least one of the handles includes a knife lockoutthat prevents the knife assembly from being actuated when the jawmembers are disposed in the second position.
 13. An endoscopic forcepsaccording to claim 12 wherein the lockout mechanism includes amechanical interface extending from at least one of the handles, themechanical interface being dimensioned to impede movement of the knifeassembly when the handles are disposed in a first open position relativeto the housing and the mechanical interface being dimensioned to permitactuation of the knife assembly when the handles are disposed in asecond position relative to the housing.